Oil recovery method utilizing a dicyclopentadiene derived ethoxysulfonate

ABSTRACT

A dicyclopentadiene derived ethoxysulfonate alone or combined with a petroleum sulfonate surfactant is dissolved in water to form an effective surfactant fluid that is stable in high salinity and/or high temperature environments. The surfactant fluid is injected into an underground petroleum-containing reservoir in an enhanced oil recovery process.

This is a division of application Ser. No. 06/423,415, filed Sept. 24,1982.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for recovering petroleum fromsubterranean formations by aqueous surfactant flooding using adicyclopentadiene derived ethoxysulfonate containing fluid. In anotherembodiment, the invention relates to a petroleum recovery fluidcomprising petroleum sulfonates and a solubilizing amount of adicyclopentadiene derived ethoxysulfonate in aqueous medium.

2. Description of the Prior Art

Crude oil which has accumulated in subterranean reservoirs is recoveredor produced through one or more wells drilled into the reservoir. In theinitial production, the crude oil is produced by primary recoverytechniques wherein only the natural forces present in the reservoir areutilized to produce the oil. However, upon depletion of these naturalforces and the termination of primary recovery a large portion of thecrude oil remains trapped within the reservoir. Additionally, manyreservoirs lack sufficient natural forces to be produced by primarymethods from the very beginning. Recognition of these facts has led tothe development and use of many enhanced oil recovery techniques. Mostof these techniques involve injection of at least one fluid into thereservoir to produce an additional amount of crude oil. Some of the morecommon methods are water flooding, steam flooding, CO₂ flooding, polymerflooding, surfactant flooding, caustic flooding, and in situ combustion.

Water flooding, which involves injection of water into the subterraneanoil reservoir for the purpose of displacing the crude oil from the porespaces of the reservoir rock toward the producing wells, is the mosteconomical and widely used of the enhanced oil recovery methods.Nevertheless, water does not displace oil with high efficiency becauseof the immiscibility of water and oil and because of the highinterfacial tension between them.

Surfactant flooding involves the addition of one or more surface activeagents or surfactants to the water flood for the purpose of minimizingthe water flooding problems mentioned above. This has been an area ofactive interest in the art of enhanced oil recovery methods for manyyears. U.S. Pat. No. 3,302,713 discloses the use of petroleum sulfonatesas effective surfactants in oil recovery operations. Other surfactantsproposed for use in oil recovery processes include alkyl sulfates, alkylaryl sulfates, alkyl or alkyl aryl ethoxy sulfates, alkyl sulfonates,alkyl aryl sulfonates, and quaternary ammonium salts.

While the above surfactants may be effective under ideal conditions,there are problems concerned with the use of each in most petroleumreservoirs. Some of the most serious problems arise from the effects ofreservoir fluid salinity on the injected surfactant solution, the mostcommon being precipitation and resultant loss of the surfactant. Thepetroleum sulfonates represent a class of surfactants that arerelatively inexpensive and that are quite effective oil recovery agentsunder certain conditions. However, when used in single surfactantsystems, they are best employed in reservoirs having brines of 10,000ppm or less total dissolved solids salinity and a very low divalent ionconcentration. Effectiveness of a petroleum sulfonate surfactant systemcan be extended somewhat by blending oil soluble petroleum sulfonateswith water soluble petroleum sulfonates. However, even a solution suchas this is not entirely satisfactory because as the blended mixture isdriven through the formation one of the components is oftenpreferentially retained within the formation matrices, causing a changein the relative concentration of the surfactant components and resultingin a failure to maintain effective salinity tolerance as evidenced byprecipitation of the surfactants.

It can be readily seen that there remains a substantial need for asurfactant flooding process that will allow the use of petroleumsulfonates in high salinity and high divalent ion concentrationreservoir environments.

U.S. Pat. No. 4,140,724, Nyi et.al., describes reactions involvingdicyclopentadiene.

SUMMARY OF THE INVENTION

The dicyclopentadiene derived ethoxysulfonate of the present inventioncan be generically represented by the formula:

    R--Y(CH.sub.2 CH.sub.2 O).sub.m (CH.sub.2).sub.n SO.sub.3 X

wherein R is the dicyclopentenyl moiety: ##STR1## Y is a divalent moietyselected from the group consisting of oxygen and sulfur,

X is a cation selected from the group consisting of sodium, potassiumand ammonium,

n is an integer of from 2 to 3,

m is an integer of from 1 to 10 with the proviso that when Y is sulfur,m is an integer of from 2 to 10.

These surface active agents may be used as the only constituent in anaqueous solution or they may be used in combination with each other orwith an anionic surfactant such as petroleum sulfonate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention concerns an improved surfactant water flooding petroleumrecovery process suitable for use in high salinity formations, e.g.,formations containing water or brine whose salinity is from 20,000 to240,000 parts per million total dissolved solids, which formation brinesfrequently also contain high concentration of divalent ions such ascalcium and magnesium in the range from 1,000 to 20,000 parts permillion. The surfactant fluid is ordinarily compounded to have about thesame salinity as the formation water, usually in the range from 50% to100% and preferably from 75% to 100% of the salinity of the waterpresent in the formation. In one embodiment, the present inventionrelates to a process for recovering petroleum from a subterraneanpetroleum bearing formation penetrated by an injection well and aproduction well which comprises:

(A) injecting into the formation via the injection well a drive fluidcomprising water having dissolved therein an effective amount of asurface active agent having the general formula:

    R--Y(CH.sub.2 CH.sub.2 O).sub.m (CH.sub.2).sub.n SO.sub.3 X

wherein R is a dicyclopentenyl moiety, Y is a divalent moiety selectedfrom the group consisting of oxygen and sulfur, X is a cation selectedfrom the group consisting of sodium, potassium and ammonium, n is aninteger of from 2 to 3, m is an integer of from 1 to 10 with the provisothat when Y is sulfur, m is an integer of from 2 to 10;

(B) forcing the fluid through the formation; and

(C) recovering petroleum through the production well.

The integer m is preferably an integer of from 2 to 6.

As previously mentioned, the fluid is typically made up in brinesolution and particular compatibility with brine has been found when Xis sodium.

The concentration of an effective amount of dicyclopentadiene derivedethoxysulfonate in aqueous solution will vary depending on theparticular homologue chosen for use as well as the water salinity andhardness and the temperature to be encountered in the formation. It ispreferred that the optimum response at various concentrations bemeasured under conditions simulating those which will be present in theformation and the concentration which corresponds to the optimumsurfactant performance characteristics be identified in this manner. Inactual field use, the concentration of surfactant used will beconsiderably greater than the optimum value determined from thecapillary displacement value in order to compensate for surfactantabsorbed by the formation. Generally the concentration ofdicyclopentadiene derived ethoxysulfonate will be from about 0.05 toabout 5.0 percent and preferably from about 0.1 to about 2.0 percent byweight.

The volume of surfactant solution to be utilized in the process of thisinvention can vary from about 2 to about 75 pore volume percent and ispreferably from about 10 to about 50 pore volume percent. It is, ofcourse desirable from an economic standpoint to use as small an amountof surfactant as possible to attain the necessary performance.

Ordinarily, the petroleum formation will have been subjected toconventional water flooding before the application of the surfactantsolution of this invention; although this is not a requirement for theapplication of the surfactant process of this invention. Water floodingis generally undertaken if it will result in the recovery of areasonable quantity of oil above that required by primary means since itis much less costly than surfactant flooding or other means of enhancedrecovery. If the surfactant flooding process is to be applied to aformation which has already been water flooded, the water sample testedshould be that existing in the formation after water flooding since theconcentration of salt as well as water soluble salts of divalent cationssuch as calcium or magnesium may be changed as a consequence ofinjecting water differing from the original formation water. As acorollary to this, the formation temperature after water flooding shouldbe ascertained since it may have been altered as a consequence of thewater flooding process. Preflushing with a sacrificial agent, e.g.,inorganic phosphate, may be useful to minimize adsorption losses of thesurfactant on the formation matrix.

It is also common practice to follow the surfactant solution with anaqueous solution which contains little or no surfactant but which hasdissolved in it a substance which increases viscosity of the water so asto attain a favorable mobility ratio between that solution and thepreviously injected surfactant solution. Hydrophilic polymers such assodium polyacrylamide or polysaccharides are commonly utilized for thispurpose. The type and quantity of viscosity increasing polymer injectedsubsequent to the surfactant solution can generally be the same as inregularly used for such purposes in conventional surfactant flooding.Generally from about 5 to about 50 pore volume percent of an aqueoussolution containing from about 100 to about 800 parts per million of thehydrophilic polymer is used. This is followed by water injection whichis continued until the water-oil ratio of the fluid being recovered fromthe formation increases to a point where further injection of water isuneconomical. It is, of course, also acceptable to increase theviscosity of the surfactant fluid by incorporation of a similar polymer.

Another embodiment of the present invention is an aqueous fluidcomprising:

(A) about 0.1 wt % to about 2 wt % of a surface active agent of theformula:

    R--Y(CH.sub.2 CH.sub.2 O).sub.m (CH.sub.2).sub.n SO.sub.3 X

wherein R is a dicyclopentenyl moiety, Y is a divalent moiety selectedfrom the group consisting of oxygen and sulfur, X is a cation selectedfrom the group consisting of sodium, potassium and ammonium, n is aninteger of from 2 to 3, m is an integer of from 1 to 10 with the provisothat when Y is sulfur, m is an integer of from 2 to 10.

(B) about 0.1 wt % to about 4 wt % of a petroleum sulfonate.

It is preferred that the petroleum sulfonate be at least partially watersoluble with an average equivalent weight at a range of from about 350to 500. The ratio of the dicyclopentadiene derived ethoxysulfonate topetroleum sulfonate should be from 0.05:1 to 1:1 and preferably from0.1:1 to 1:1.

The water which makes up the aqueous medium of the fluid mixture of thisinvention may be either hard or soft. The invention has been found to beparticularly useful in hard water such as brine which containsconsiderable amounts of divalent ions. That is, the invention isespecially effective for stabilizing aqueous surfactant solutions inwhich the aqueous medium contains considerable amounts of calcium and/ormagnesium ions and is considered hard water. It is in these hard watersthat some surfactants are particularly prone to be unstable. It is knownin the art that surfactants such as petroleum sulfonates are not at allcompatible with calcium and magnesium ions in hard water. Recentdiscoveries have shown that the sulfonates of alkylene oxide adducts ofsubstituted phenols are compatible with calcium and magnesium ions inhard water or brine but their stability, that is their ability to remainin solution under all conditions of temperature and water hardness andsalinity, is at times a problem.

The present invention while including all types of water is particularlydirected to hard water brines. Hard water may be defined as an aqueoussolution containing from 100-20,000 parts per million polyvalent metalions such as calcium and/or magnesium ions. Brines contain a minoramount to 25% by weight sodium chloride and many contain various amountsof other dissolved salts such as sodium bicarbonate, sodium sulfate, andsodium borate. The invention is operable in hard water, brines or hardwater brines.

The water may also contain dissolved nitrogen, hydrogen sulfide, carbondioxide, methane or other gases.

The various materials available under the general name of petroleumsulfonates vary in composition according to the petroleum fraction usedfor sulfonation and in the degree of sulfonation imparted to thepetroleum fraction. Preferable petroleum sulfonates are those preparedfrom a petroleum fraction whose boiling range is from 700° F. to 1100°F. which corresponds to a molecular weight range of from about 350 toabout 500. The sodium salt of the sulfonated product of this petroleumfraction is an excellent material for use in the present invention. Thepotassium and ammonium salts are also useful.

Mixtures of petroleum sulfonates can also be employed in the fluid ofthe present invention. For example, a mixture of predominantly watersoluble petroleum sulfonate having an average equivalent weight of lessthan 400 and preferably less than 350 may be utilized along with asecond petroleum sulfonate which is at least partially oil soluble andhaving an average equivalent weight of about 400 to about 600 andpreferably about 450 to about 550.

It has been found that the degree of solubility of the surfactantcomposition in the field water is extremely critical to the oil recoveryefficiency in the process. If the surfactant is much more soluble inwater than oil, then the surfactant tends to be distributed throughoutthe bulk of the water phase including both formation water and injecteddrive water, and little effectiveness will be achieved at theinterfacial zones between oil and water. Similarly, if the surfactant issubstantially more soluble in oil than it is in water, the surfactantwill partition into and distribute itself throughout the oil phase, andwill have little effect on the surface tension existing at theinterfacial zone between oil and water. The optimum surfactanteffectiveness is achieved if there is a condition of borderlinesolubility of the surfactant fluid in the drive water and/or formationwater, so that the surfactants tend to exist in higher concentrations atthe interfacial zone between oil and water than in either the oil phaseor the water phase.

It has been found that when using blends of petroleum sulfonates and thedicyclopentadiene derived ethoxysulfonate of the present invention,optimum oil recovery efficiency occurs when the concentrations of thematerials were carefully balanced so as to produce a condition ofborderline solubility. If too little solubilizing cosurfactant is used,the primary surfactants are rendered insoluble and at least a portionthereof will precipitate in the aqueous solution. This can, as discussedabove, result in at least reducing the effectiveness of the surfactantfluid for the purpose of recovering oil, and may lead to permanent,irreversible damage to permeability of the formation matrix, which willprevent any further displacement of petroleum from the formation. On theother hand, if more than the minimum amount of solubilizingdicyclopentadiene derived ethoxysulfonate which achieves the conditionswhich we have described above as borderline solubility is used incombination with petroleum sulfonate, the surfactants are rendered toosoluble in the aqueous phase and the amount of oil displaced by such asolution being injected into a formation is reduced fairlysubstantially. Moreover, since the cost of the dicyclopentadiene derivedethoxysulfonate is high compared to that of petroleum sulfonate, theresult of using too much solubilizing dicyclopentadiene derivedethoxysulfonate is that the fluid cost is increased and the amount ofoil recovered by the use of the fluid is decreased, with rapidlydiminishing economic attractiveness of the process.

The amount of solubilizing dicyclopentadiene derived ethoxysulfonate toachieve the above described desired condition of borderline solubilityis highly dependent on all of the possible variations in the structuralcharacteristics of the surfactant molecules employed. The averageequivalent weight of the petroleum sulfonate for example, will affectthe amount of dicyclopentadiene derived ethoxysulfonate required toachieve the condition of borderline solubility. For example, any changein the number of ethylene oxide groups condensed with the molecule, willchange the amount of dicyclopentadiene derived ethoxysulfonatecosurfactant needed to achieve the condition of borderline solubilitywith whatever primary anionic surfactant or mixture thereof it is used.Furthermore, the aqueous fluid salinity and the concentration ofdivalent ions present in the fluid will also determine the amount of thesurfactants needed to achieve borderline solubility. Generally, highersalinity and/or higher concentrations of divalent ions of the aqueousfluid in which the surfactants are dissolved require increasing numberof ethylene oxide units to be present on the solubilizing cosurfactantmolecule.

It has been found that one satisfactory method for determining theproper concentrations of petroleum sulfonate and dicyclopentadienederived ethoxysulfonate is found in U.S. Pat. No. 4,066,124 which isincorporated herein in its entirety by reference. By this method it hasbeen found that brine solutions of about 0.1 wt % to about 2 wt % of thedicyclopentadiene derived ethoxysulfonate of the present invention andabout 0.1 wt % to about 4 wt % of a petroleum sulfonate herein definedproduce advantageous results in an enhanced oil recovery process. Theseadvantageous results include applications where hydrolytically andthermally stable surface active agents soluble in salt solutionscontaining divalent cations is required. Advantageous results are alsoachieved where relatively viscous solutions or emulsions are desired.

One unexpected advantage of the dicyclopentadiene derivedethoxysulfonate of the present invention is the surprising stability andviscosity displayed by some of the compounds over a wide range ofsalinities and temperatures.

Another surprising advantage of the present invention is that good oildisplacement results when the dicyclopentadiene derived ethoxysulfonateof the present invention is used as a solubilizer of petroleumsulfonates in an oil recovery process. A 10-carbon moiety usually isinsufficiently hydrophobic to prepare true surfactants. The borderlinesurfactant character of the dicyclopentadiene derived sulfonates of thepresent invention is confirmed by antagonistic titration results withcationic surfactants.

In another embodiment, the present invention relates to a composition ofmatter characterized by the formula:

    R--Y(CH.sub.2 CH.sub.2 O).sub.m (CH.sub.2).sub.n SO.sub.3 X

wherein R is a dicyclopentenyl moiety, Y is a divalent moiety selectedfrom the group consisting of oxygen and sulfur, X is a cation selectedfrom the group consisting of sodium, potassium and ammonium, n is aninteger of from 2 to 3, m is an integer of from 1 to 10 with the provisothat when Y is sulfur, m is an integer of from 2 to 10.

The integer m is preferably an integer of from 2 to 6. Sodium is apreferred cation.

Compounds of the present invention may be prepared according to thefollowing sequence: ##STR2##

Synthesis of the compounds of the present invention is more fullydescribed in the Examples.

Use In Enhanced Oil Recovery

The surfactant fluid is preferably prepared in formation water or fieldwater having a salinity and divalent ion concentration about equal tothe formation water. The quantity of surfactant fluid utilized willgenerally be from 0.1 to 1.0 pore volume based on the pore volume offormation to be swept by the surfactant fluid. The surfactant fluidshould be followed by injection of a mobility buffer, which is anaqueous solution of a hydrophilic, viscosity increasing polymer such aspolyacrylamide or polysaccharide. Generally from 50 to 1000 parts permillion polymer concentration is sufficient to produce a fluid having aviscosity greater than the formation petroleum viscosity, which isadequate to ensure efficient displacement. From 0.1 to 0.5 pore volumesof the viscous mobility buffer solution are used. This is in turnfollowed by injection of field water to displace all of the injectedfluids and petroleum through the formation to the production well. Fieldwater injection is continued until the oil cut of the produced fluiddrops to an uneconomic level.

This invention is more fully illustrated by the following Examples:

EXAMPLE I

A. One mole of ethylene glycol was added to the norbornyl double bond ofdicyclopentadiene using a BF₃ -diethyl ether complex as catalyst. To 474grams of the adduct obtained were added 3 grams of potassium hydroxideand after stripping of water, 215 grams of ethylene oxide at 100° C. to130° C. Hydroxyl number analysis of the product confirmed the structureas the mono(dicyclopentenyl) ether of triethyleneglycol.

B. A one liter resin flask was charged with 600 grams of the product ofExample I-A and 5.4 grams of potassium hydroxide and the mixture washeated to 180° C. at 120 mm Hg pressure with good mechanical stirring.Then, 300 grams of a 56% aqueous solution of HOCH₂ CH₂ SO₃ Na wasintroduced dropwise over a 21/2 hour period under these conditions whileremoving water overhead. The mixture was digested at 180° C. and 120 mmHg for an additional 45 minutes and then cooled to room temperature.Then the crude reaction mixture was taken up in 1000 grams of water andextracted successively with 1700 grams, 1000 grams, 1000 grams and 500grams of ethyl acetate to remove unreacted nonionics of which 265 gramswas recovered.

The aqueous solution was distilled to completely remove dissolved ethylacetate, leaving 1010 grams of aqueous product solution containing 24.2wt % of the desired product sulfonate and 53.7 wt % water.

The product was determined to have the formula: ##STR3##

EXAMPLE II

By the method of Example I-A, 2.6 moles of ethylene oxide was added tothe reaction product obtained by free radical addition of one mole ofbeta-hydroxyethylmercaptan to dicyclopentadiene. This product (450grams) was charged to a one liter resin flask with 4 grams of potassiumhydroxide and 245 grams of a 56% aqueous solution of HOCH₂ CH₂ SO₃ Nawas added over 2 hours under conditions described in Example I-B. Thismixture was digested at 180° C. and 120 mm Hg for 1 hour and thenextracted as described in Example I-B. Workup yielded 843 grams ofaqueous solution containing 26.2 wt % by titration of the desiredsulfonate.

The product was determined to have an average formula of: ##STR4##

EXAMPLE III

A. A one liter flask was charged with 304 grams of the ethylene glycoladduct of dicyclopentadiene which was prepared using a BF₃ -diethylether complex as mentioned in Example I. The flask was heated to 110° C.with mechanical stirring. To the flask was added a solution of 65 gramsNaOH in 110 grams of water over about a half hour with nitrogen purgingwhile maintaining a pressure of about 1 to 10 mm Hg. The mixture wasdigested for 2 hours under vacuum at 110° C. and then 110 g. of allylchloride was added over 3 hours at 80° C. to 85° C. Enough excess allylchloride was removed overhead to raise the reflux temperature to 120°C., followed by vacuum stripping at this temperature. To the remainingreaction mixture were added 250 ml water and 100 grams of isopropanol.The aqueous layer was discarded and the organic layer stripped to removesolvent, leaving 278 grams of partially allylated etherdicyclopentenoxyethanol, identified by nmr spectroscopy.

B. A round bottom flask equipped with mechanical stirrer, air inlet tubewith fritted disk, reflux condenser, thermometer, dropping funnel and pHprobe was charged with 25 grams of the allyl ether of Example III-A, 150grams of isopropyl alcohol, 125 grams of water and 8 grams of aqueous20% sodium hydroxide solution. The mixture was stirred at 55° C. with anair flow of 30 ml/min while metering in an aqueous 33.3% sodiummetabisulfite solution at such a rate as to maintain solution pH at 7.2.An additional 100 grams of the allyl ether of Example III-A was slowlyadded over the first hour of reaction. After 8 hours, 147 grams ofbisulfite solution had been added and the pH began dropping.

The reactor was shut down and 50 grams of isopropyl alcohol was added.The bottom layer which contained the bulk of the inorganic salts wasremoved. The top layer was stripped to remove isopropyl alcohol. Theresidue was dissolved in 100 grams of water and extracted with 580 gramsof ethyl acetate in three portions to recover 42 grams of unreactednonionics.

The aqueous layer was distilled to remove dissolved ethyl acetate,leaving a 275 gram solution of the desired propane sulfonate, identifiedas ##STR5##

The solution contained a calculated 39 wt % sulfonate based on unreactedstarting materials but only gave a value of 16.2% by antagonistictitration with cationic surfactant, indicating the borderline surfactantproperties of the compound.

EXAMPLE IV

A. The compound R--S(CH₂ CH₂ O)₁ (CH₂)₃ SO₃ Na was prepared from themercaptoethanol adduct of dicyclopentadiene, allyl chloride and sodiumbisulfite using the method of Example III. The product solution wasfound to contain 22.6% desired sulfonate with a titration value of 16 wt%.

B. A solution of R--S(CH₂ CH₂ O)₂.3 (CH₂)₃ SO₃ Na (38 wt % calculatedsulfonate, 26.1 wt % by titration) was prepared by the method of ExampleIII on the 1.3 molar ethoxylate of the mercaptoethanol adduct ofdicyclopentadiene.

C. A solution of R--S(CH₂ CH₂ O)₂.9 (CH₂)₃ SO₃ Na (44 wt % calculatedsulfonate, 30.7 wt % by titration) was prepared using the method ofExample III on the 1.9 molar ethoxylate of the mercaptoethanol adduct ofdicyclopentadiene.

D. Three moles of propylene oxide were added using standard alkoxylationconditions to dicyclopentenyl alcohol. This product was reacted firstwith allyl chloride and then with sodium bisulfite using the method ofExample III. The resulting product, product of Example IV-D, contained14.8 wt % desired propane sulfonate by calculation. The titration valuewas 4.9 wt %. The structure of the resulting compound was determined tobe R--O(CH₂ CH(CH₃)O)₃ (CH₂)₃ SO₃ Na.

E. Screening tests were conducted to test the ability ofdicyclopentadiene derived ethoxysulfonates to solubilize petroleumsulfonates in brine. Screening tests for all of the solubilizers wereperformed in the same manner to allow a direct cross-comparison. Thesurfactant system consisted of three components(TRS-18/TRS-40/solubilizer) in different proportions to form solutionswith a total of 2.5% weight active surfactant. TRS-18 is an oil solublepetroleum sulfonate of average equivalent weight 502 and an equivalentweight range of 353 to 640. TRS-40 is a water soluble petroleumsulfonate of average equivalent weight 337 and an equivalent weightrange of 273 to 440. Both TRS-18 and TRS-40 are products of WitcoChemical Company.

The solutions contained 85,000 ppm of dissolved salts and this was keptconstant by adding a fixed quantity of simulated Slaughter 2 fieldproduced brine. Deionized water was then added in varying amounts tomake a total weight of 50 grams for each sample. The mixtures werestirred with heating and then aged overnight. After aging, the solutionswere observed for phase stability. Stable solutions were tested forcapillary displacement at room temperature with Slaughter stock tank oilthinned to reservoir viscosity by heptane addition (25 volume percentheptane).

Solubilized systems incorporating the products of Examples I, II, III orIV-C showed large areas of phase stability and moderately large areas ofcapillary displacement activity on ternary diagrams. The products ofExample IV-A and IV-D showed no ability to solubilize petroleumsulfonates. The product of Example IV-B showed good performance incapillary tests and continuous surfactant core floods; however, a largevolume of surfactant was required.

EXAMPLE V

In a field in which the primary production has already been exhausted,an injection well is completed in the hydrocarbon-bearing formation andperforations are formed between the interval of 6890-6910 feet. Aproduction well is drilled approximately 415 feet distance from theinjection well, and perforations are similarly made in the samehydrocarbon-bearing formation at 6895-6915 feet.

The hydrocarbon-bearing formation in both the injection well and theproduction well is hydraulically fractured using conventionaltechniques, and a gravel-sand mixture is injected into the fracture tohold it open and prevent healing of the fracture.

In the next step, oil field brine of 1000 ppm hardness at a temperatureof 75° F. containing dissolved therein 1% by weight petroleum sulfonateand 0.5% by weight of the product of Example I is injected via theinjection well into the formation at a pressure of about 1300 psig andat the rate of 1.05 barrels per minute. Injection of the driving fluidcontinues at the rate of 1.05 barrels per minute and at the end of 67days, a substantial production of petroleum is achieved.

The principle of the invention and the best mode contemplated forapplying that principle have been described. It is to be understood thatthe foregoing is illustrative only and that other means and techniquescan be employed without departing from the true scope of the inventiondefined in the following Claims.

What is claimed is:
 1. A composition of matter of the formula:

    R--Y(CH.sub.2 CH.sub.2 O).sub.m (CH.sub.2).sub.n SO.sub.3 X

wherein R is a dicyclopentenyl moiety, Y is a divalent moiety selectedfrom the group consisting of oxygen and sulfur, X is a cation selectedfrom the group consisting of sodium, potassium and ammonium, n is aninteger of from 2 to 3, m is an integer of from 1 to 10 with the provisothat when Y is sulfur, m is an integer of from 2 to
 10. 2. Thecomposition of matter of claim 1 wherein m is an integer of from 2 to 6.3. The composition of matter of claim 1 wherein X is sodium.
 4. Thecomposition of matter of claim 1 wherein Y is oxygen, m is 3, n is 2 andX is sodium.